The multimedia units are defined herein as desktop or portable personal computers, digital television decoders, television sets or portable phones etc. to which a conditional access and decryption module is connected. More particularly, the object of the invention concerns the updating and managing the software of the conditional access module as well as the data streams processing application installed in the multimedia unit.
Many digital television decoders, as well as television sets with an integrated digital receiver and personal computers equipped with adequate interfaces, use a conditional access module CAM (Conditional Access Module) to control access to the broadcast audio/video digital data and to descramble these data. Typically, this module is in form of a detachable standardized case provided with a smart card reader and a connector compatible with an interface of the computer. An example is described in the U.S. Pat. No. 6,443,361. Such a CAM module provided by a Pay-TV operator descrambles one or more audio/video data streams coming from a cable, a terrestrial radio waves transmitter, a satellite, an Internet server via a wired or wireless communication network (WebTV, IP TV) with keys or control words received from an element dedicated to the conditional access. This element, in charge of the security of the decryption of the descrambling keys and conditional access rights, consists generally of a tamper-proof smart card or security module, inserted in the reader of the conditional access module CAM, wherein user rights are stored. Messages included in the broadcast streams consisting of control messages ECM (Entitlement Control message) and rights administration messages EMM (Entitlement Management Message) are directed towards the security module storing the transmission keys necessary for decrypting these messages. The control words (CW) included in the control messages ECM are decrypted, and, returned to the descrambling module if and only if the conditional access rights are present and verified by the security module.
A CAM module is generally connected to the host multimedia unit via a common interface DVB-CI (Digital Video Broadcasting-Common Interface) defined by the European Standard EN50221 “Common Interface Specification for Conditional Access and other Digital Video Broadcasting Decoder Applications” edited by the CENELEC (European Committee for Electrotechnical Standardization). This document describes a common interface while standardizing the data structure, the channel coding, the service information, and the interface with the host unit and with the conditional access system. The latter is used to control the access to a broadcast service consisting of a set of elementary streams offered to the user in a form of a television program for instance. According to this document, the CAM module carries out applications by communicating with the host unit and providing to the user functionalities complementary to those included in the host unit such as the conditional access system or an electronic program guide. Furthermore, it is compatible with the PCMCIA format (Personal Computer Memory Card International Association), USB (Universal Serial Bus) or others.
According to a compact configuration, the CAM module may be in form of a “dongle” or an electronic key comprising both the security module and the decryption module integrated in one or more electronic circuits. This “dongle” is connected to a port of the computer for communication towards external peripherals such as the parallel port, the USB serial port, the IEEE1394 Firewire port, etc. An example of application of a “dongle” for the access control to encrypted data is described in the document US2007256126.
The multimedia unit comprises a particular application of the type Windows Media Player, Real Player, VLC Media Player etc. intended to use or view the content of the broadcast data obtained after decoding. This application is secured in association with the conditional access module CAM in order to control records, transfers or copies of the content on local or distant supports to prevent abuses. Moreover, it is not desirable to allow a third application to process the received data without the authorization of the broadcaster or, the operator controlling the access to this data.
A standard such as CableCard (SCTE41 www.scte.org) can be used to secure the audio-visual data stream between the conditional access module and the multimedia unit. Nevertheless, such a solution needs rigorous and secured management of the keys and algorithms within the multimedia unit, which is difficult to ensure over a long period particularly in the case of open architectures which may be used on personal computers.
Therefore, it is desirable to guarantee a reliable and secure coupling of the application or the operating software installed in the multimedia unit processing the decrypted content with the software or firmware of the secured conditional access module CAM.